1. Field of the Invention
This invention relates to mechanical devices for spreading powders. More particularly it is directed to a device for spreading coherent powder and comprising a bin with a foraminous wall discharge area and a cylinder of resilient reticulated foam disposed to force the powder through the perforations of the foraminuous wall upon rotation.
2. Prior Art
Feeding of powders for deposition in a uniform manner on a substrate has been practiced in the distribution of fertilizers, insecticides and like materials on lawn and farm areas and in the distribution of toners in xerographic copiers. Early rotating brush devices are exemplified by U.S. Pat. No. 1,191,116, while U.S. Pat. No. 3,250,439 discloses the use of a resilient polyurethane pad to push out toner by moving along a row of holes in a discharge plate, and U.S. Pat. Nos. 3,596,807; 3,608,792; 3,128,015 and 3,172,574 disclose a resilient open-celled elastomeric roll which rotates against a slit in the bottom of a bin. Such powders are generally quite dry and do not offer problems of the magnitude found in distributing powders containing a significant amount of liquid. Such liquid-containing powders are coherent and coherent powders tend to bridge the openings through which they must pass and may not feed at all, or may be deposited intermittently in a very uneven pattern. The feed rate of these prior art feeders is unduly sensitive to the moisture content of the coherent powder. The device of this invention overcomes these inadequacies by providing a feeder which utilizes a cylinder of reticulated resilient foam which transports and urges coherent powder through perforations in a discharge plate.